Hydraulic system, including a cooling circuit for the pumps thereof



F. J. WRIGHT Dec. 16, 1952 HYDRAULIC SYSTEM, INCLUDING A COOLING CIRCUIT FOR THE PUMPS THEREOF Original Filed April 21, 1948 l/vvs/vroe FEED J. WEI GH BY amm Patented Dec. 16, 1952 HYDRAULIC SYSTEM, INCLUDING A'COOL- ING CIRCUIT FOR THE PUMPS THEREOF Fred J. Wright, Columbus, Ohio, assignor to The Galion Iron Works & Manufacturing Company, a corporation of Ohio @riginal application April 21, 1948, Serial No.

1950, Serial No. 154,790

2 Claims.

This invention relates to hydraulic systems.

It is an object of the invention to provide an improved hydraulic system wherein there is included a substantially closed hydraulic circuit having a high pressure and a high volume pump and a hydraulic motor driven thereby, fluid in the closed circuit being recirculated, and a second hydraulic circuit including a hydraulic pump adapted to discharge hydraulic make-up and cooling fluid into said substantially closed circuit whereby all of said make-up and cooling fluid is supplied to the engine of the high volume and high pressure pump, and its addition to the substantially closed hydraulic circuit causes displacement of hot hydraulic fluid therefrom.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

The accompanying drawing illustrates diagrammatically the hydraulic system of a threewheeled trench roller that embodies the features of my invention.

This application is a division of my application, Serial No. 22,390, filed April 21, 1948, for a Motorized Trench Boiler, and only so much of the trench roller will be described here as is necessary to an understanding of the function of the hydraulic motors of the hydraulic system shown in the drawing.

The trench roller that embodies the hydraulic system shown in the drawing is a three-wheeled or tricycle type roller that includes at one side a wide rimmed roll. At the side opposite the Wide rimmed roll it includes a bicycle unit, the wheels of which when in tandem posit-ion are reversely steerable to steer the roller when the roll is rolling material and whichmay be swung to parallel positions in order that the wide rimmed roll may be carried by a towing vehicle and the roller towed as a two-wheeled trailer.

The main frame of the roller includes two spaced rigid frame parts, one of which carries the wide rimmed roll and the other of which in effect forncs the frame of the bicycle unit. These two spaced rigid side frame parts are connected by struts pivoted to each of them so as to form an adjustable parallelogram main frame for the entire trench roller. The wheels of the bicycle unit or portion of the trench roller are swung for steering purposes and to their parallel positions by the hydraulic motor indicated at 62 in the drawing, and the main frame of the roller is ad- .justed as a parallelogram to change the elevation of the planes in which the axes of the wheels of the bicycle unit and the axis of the wide rimmed Divided and this application April 8,

2 roll lie, by the motors indicated at 4i in the drawing. The wide rimmed roll is driven by a reversible rotary hydraulic motor indicated at 72 in the drawing, and the roll is provided with brake mechanism including abrake drum .95 and 'a brake band 91.

The hydraulic system includes a closed high pressure and high volume hydraulic circuit which includes a high pressure variable delivery roversible pump Iid which is capable of being .adjusted from a .zero output volume to alarge or hi h output volum of hydraulic fluid under high pressure. The high pressure andhi'gh volume hydraulic circuit also includes a high pressure and high volume reversible radial type hydraulic motor 12 that reversibly drives the roll. Conduits Ice and Iill connect the high pressure variable delivery reversible pump no with the motor F2. The pump Ilil, as indicated in th drawing, is discharging or pumping hydraulic fluid into the conduit It!) to drive the roll motor 72. Conduit It! conducts the hydraulic fluid exhausted from the motor '32 to the port of the pump Ill"! acting as the intake or suction port thereof.

The hydraulic fluid in the closed circuit including pump lit, conduit I80, motor I2 and conduit ISI is recirculated; that is, fluid exhausted by the motor I2 flows back to the pump IIc through the conduit ItI and is pumped by the pump IIO through-conduit I00 back to the motor I2. The output volume of pump IN] may be varied from zero to a high volume and the pump IIEI includes a rotor I II having reciprocating vanes I I2 that operate in a ring or housing H3, the axis of which may be shifted with respect to the axis of the rotor II I. It will be seen, of course, that when the axis of the rotor I I I and the axis of the ring or housing II3 coincide, the pump Ht will not be operating to produce any output of hydraulic fluid either into the conduit Ice or IGI. In order to cause the pump IN) to pump hydraulic fluid the axis of ring or housing II3 may be shifted or ofi-set with respect to the axis of rotor III either to the right or left, and the amount of off-setting of these axes determines the output volume of pump IN If the ring or housing I I3 is shifted to the left, as indicated in the drawing, the pump I It will discharge into conduit I80, and if the ring or housing I13 is shifted to the right, the pump Ht will discharge into conduit I83 I. The ring or housing I I3 is shifted to the right by a piston motor H4 and to the left by a piston m-otor H5.

The entire hydraulic system also includes a tank 26 which is a reservoir for hydraulic fluid used in the hydraulic system. From the hydraulic tank 23 a supply conduit H3 leads to a low volume low pressure constant delivery pump II1. In the trench roller shown and described in my co-pending application, Serial No. 22,390, above identified, pumps H8 and H1 are both contained within a pump unit 25 and both may be driven from the same shaft, which shaft is driven by an internal combustion engine, not shown. The hydraulic fluid pumped by pump H1 is conducted through a conduit H3 into one end of a control valve unit 56. For the moment it will suffice to say of the control valve unit 56 that hydraulic fluid normally passes through it and is discharged from the opposite end thereof into a conduit I I 9 that leads to conduits I 24 and I2I which connect res ectively with conduits IN and IE5.

Conduit I2I includes a check valve I22 and conduit I2 includes a check valve I23. When the closed hydraulic circuit inc uding pump IID, motor 12 and conduits IIlII and IGI is operating, as previously described. the outp t of hydraulic fluid pum ed by pump II is supplied to motor 12 through conduit I02 and the pressure in conduit I02 will close the check valve I22 in conduit I2I. Conduit IIlI which is acting as the low pressure conduit of the closed system and through which hydraulic fluid is being conducted from the motor 12 to the intake or suction port of motor IIil will be subjected to a relatively low hydraulic pressure, and check valve I23 in conduit I2l will open under pressure of the hydraulic fluid pumped by pump H1 in conduits IIS and I2 to admit the hydraulic fluid pumped by pump II1 to the conduit IIlI. It will be seen, of course, that the volume of hydraulic fluid flowing into conduit IBI will be considerably less than the volume of the hydraulic fluid discharged from th motor 12 when pump III! is operating at full capacity, but it will also be seen that an amount of hydraulic fluid substantially equal to the amount added by the pump II1 to the conduit IIlI must be displaced from, the low pressure conduit IIlI.

It will be seen also that when the output volume or pressure of pump III) is directed into conduit IBI the pressure in conduit IIlI will close check valve I23, and check valve I22 in conduit I2I will open to pass the hydraulic fluid pumped by pump II1 into the conduit IGIl, acting as the low pressure or suction side of the high pressure closed system. In order to permit hydraulic fluid to be displaced from the conduits IIlI and IIlil there is connected to the conduits IUI! and IIlI of the high pressure high volume closed circuit a shiftable spool type valve I24.

Valve I24 includes a body I25 having a central bore I26 in which there is slidably received a piston or spool I21. The ends of body I25 are closed by caps I28. The body I25 of valve G24 includes a threaded opening I29 that receives a conduit I33 connected to the conduit I34, and the body I25 includes another threaded opening I31 that receives a conduit I32 connected to conduit I31. Threaded opening I29 connects with an annular channel I33 formed in the bore I26, and the threaded opening I3I connects with another channel I34 in the bore I26. Spaced outwardly of channel I33 in an annular channel I35 that connects with a threaded exhaust opening I35 in the body I25 and spaced outwardly of the annular channel I34 is an annular channel I31 that is also connected with the threaded exhaust opening I36. Threaded exhaust opening I36 receives a. conduit I44 in which there is interposed a pressure relief valve I38. Valve I24 is a conventional valve well known to those skilled in the art and in actual construction this valve includes an annular groove positioned centrally of the bore I23 that is connected with a threaded opening in the side of body I25. This central annular groove is unnecessary to the present invention and therefore the port communicating with it is closed by a pipe plug.

The piston I21 of valve 124 includes three spaced lands I33, I49 and I45. Lands I33 and I49 are connected by a reduced diameter portion I42 of the piston I21, and lands I48 and MI are connected by a reduced diameter portion I43 of the piston I21. The lands are so spaced that when the piston I21 is moved downwardly, as shown in the drawing, the annular channel I34 connected with opening I3I is connected through the bore I23 with the circular opening I31 which in turn is connected to the conduit 44 that leads through the pressure relief valve I38 and to the tank or reservoir 26. The spacing of lands I33 and I48 on piston I21 is also such that when the piston I21 is positioned, as seen in the drawing, to place the annular channels I34 and I31 in communication, the communication between the annular channels I33 and $35 is blocked by the land I33. When the piston I21 is shifted upwardly to its top position the channel I34 will be isolated by the land I4I from the channel I31 to block the flow 0f fluid through the conduit I32 and this occurs when conduit IilI is acting in the high pressure side of the closed hydraulic circuit.

The piston or spool I21 is shifted from either of its positions described to the other by the diiferential of hydraulic pressures in the conduits Iilil and It. A control conduit I45 connects conduit I32 and consequently conduit I00 with a chamber I46 in valve I24 formed by the cylinder head I28, the bore I26 and the head of piston I21 adjacent land I39, and a conduit I41 connects conduit I32 and consequently conduit IIII with a chamber I43 in valve I24 similar to chamber I46 but at the opposite end of piston I21.

It will be seen that if conduit IEII is placed, by reversing the output of pump I Ill, in the high pressure side of the closed circuit, conduit I41 will admit fluid under pressure into chamber I48 to force the piston I21 upwardly which, of course, will cause the land I4I to block the channel I31 to stop the flow of hydraulic fluid from the conduit I32 to the exhaust conduit I44 and that the fluid in chamber I46 will be displaced through conduit I45 into conduit I33 which will be con nected by the shifting of the piston I21 through channel I33, bore I26 and channel I35 to the conduit I44. Thus either conduit I or IEII when placed in the high pressure side of the closed circuit will be stopped or closed off from the conduit I44 by the valve I24, and the conduit I62 or IflI which is acting as the low pressure side of the closed circuit will be opened by the valve I24 to conduit I44 which is connected to the tank 26 through the pressure relief valve I38.

As previously described, when the conduit IOI is in the low pressure side of the closed circuit a volume of hydraulic fluid substantially equal to the volume of hydraulic fluid placed therein by pump II1 must be displaced therefrom and because conduit IGI is connected to valve I24, conduit I44 and pressure relief valve I38 to tank 26, hydraulic fluid may be displaced from the cggiduit IIII by opening the pressure relief valve The hydraulic fluid supplied to the closed hydraulic circuit of motor I2 and pump I I by pump II'I will be at a lower temperature than the hydraulic fluid exhausted from the motor I2 and thus it will act as a cooling medium or fluid for the high pressure closed circuit. It will also act as make-up fluid, that is, it will replace in the high pressure closed circuit anyhydraulic fluid lost therefrom through the glands, joints, and the likeof pump II 0 and motor I2.

It is important to note that the hydraulic fluid pumped by pump Ill into the high pressure closed hydraulic circuit enters the circuit between that port of the motor I2 that is acting as the exhaust port and that port of the pump I I0 that is acing as the intake, low pressure or suction port. This arrangement insures that all of the cooling and the make-up hydraulic fluid pumped by pump IIJI will flow together with some hot hydraulic fluid discharged by the motor 12 to the pump H0 when the latter is operating at a high output volume whereby the temperature of the hydraulic fluid entering the pump'IIO will be substantially lower than the temperature of the, hydraulic fluid passing from the exhaust port of the motor I2. Throughout all speeds at which the motor I2 is operating the cooling and make-up hydraulic fluid pumped by pump III will cause hot hydraulic fluid to be displaced from the low pressure side of the high pressure closed circuit through the pressure relief valve I33.

It will be seen, of course, that if motor I2 is being driven at such speed or is adjusted so that the intake volume of pump H0 is less than the output volume of pump II? the entire supply of hydraulic fluid for pump H0 will be comprised of the hydraulic fluid pumped by pump Hi, and the volume of hydraulic fluid pumped by pump II! which is in excess of the intake volume required by pump H0 will be discharged through valve I24, conduit I45 and pressure relief valve I38 to the tank 26. Pressure relief valve I35 is adjusted to open at a relatively low pressure and it functions to insure that at all times the conduits comprising the low pressure side of the high pressure closed circuit are maintained filled with hydraulic fluid.

The hydraulic circuit shown in the drawing also includes a low pressure circuit of which tank 26, conduit H6, pump III, conduit H8, the hydraulic control valve unit 56, and conduit H0 form a part. In addition to the function of the low pressure circuit of supplying cooling and make-up fluid to the closed high pressure circuit, the low pressure circuit functions as a control circuit to operate the motors ll, the steering motor 62, a double acting brake cylinder motor I49 associated with the brake band 91, and the piston motors H4 and H5 of the high pressure variable delivery pump H0. All of the motor units in the low pressure circuit are controlled by individual valves of the control valve unit 56. The control valve unit 56 is fully described and claimed in my Patent No. 2,486,087, granted October 25, 1949, for a Hydraulic Valve, and therefore is described only briefly here.

As previously set forth hydraulic fluid pumped by the pump I I1 normally flows through the control valve unit 56 and is discharged therefrom into conduit H9. The control valve unit 56 is comprised of a plurality of identical individual banked valves of the spool or shiftable core type, and one of the valves of the control valve unit 56 is indicated at I53. Valve I50 controls both of the piston motors I I4 and I I5 of pump I I0. The construction of valve I50 is such that when its control lever I5I is moved to one position, hydraulic fluid flowing therethrough from the conduit H8 is diverted into a conduit I52 that leads to the cylinder head of motor H5 and this hydraulic fluid operates the piston motor I I5 to move or shift the ring or housing H3 to theright. Movement of the ring or housing H3 to the right causes the piston of piston motor H4 to displace hydraulic fluid in the cylinder thereof through a conduit I53, which fluid enters the body of the valve I50 and is caused to flowthrough the other valves of the unit and into the conduit H9.

When the control lever I5I of valve. I50 is moved in the opposite direction the flow of hydraulic fluid is reversed from that described .in the conduits I52 and I53 to shift the ring .or housing I I3 to the left and when the controllever I5I of valve I50 is in a central or neutral position the conduits I52 and I53 are blocked whereby the piston motors I I4 and I I5 will be locked to maintain the ring or housing H3 in adjusted position. It is the shifting and positioning of the ring or housing H3 with respect to the rotor III which affects the output volume of hydraulic fluid being pumped by pump H0 which, of course, controls the speed of operation of motor I2 as well as its direction of operation for driving the roll of the trench roller.

The control valve unit 56 includes three other valves I55, I55 and I56, all identical in construction with valve I50. Valve I54 controls the operation of the expandable and contractable or double acting hydraulic piston motors II, which piston motors are connected in parallel and to the valve I56 by conduits I51 and I58. Valve I55 controls the operation of the steering motor 62 through conduits I59 and I60. The valve I56 controls the double acting piston motor I49 associated with the brake band 9'! for positively contracting it about the drum 96 and for positively expanding it therefrom. The valve unit 56 includes a drain conduit for collecting hydraulic fluid that might support its cores or spools, and this drain conduit is connected by a conduit I62 that returns the hydraulic fluid to the tank 26.

From the description of the valve unit 56 herein given it will be seen that when hydraulic fluid is diverted, for example, from conduit H8 by the valve I56 into conduit I52, a volume of hydraulic fluid substantially equal to the volume of fluid diverted into conduit I52 will be supplied through conduit I53 from the piston motor I It to the conduit II 9 and thus the flow of hydraulic fluid through conduit H9 will be uninterrupted. Because all of the valves I50, I54, I55 and I56 are alike, when any one of them is actuated to divert hydraulic fluid to one of the control motors, then a volume of fluid substantially equal to that diverted by the valve to the motor which it controls will also be displaced from the motor through the valve and into the conduit I I9. The structure of the valves is such that any two or all of them may be operated to control simultaneously their respective motors.

All of the motors controlled by the individual valves of valve unit 56 are expandable and contractable piston and cylinder type motors and by referring to the motors 5? for an example it will be seen that should the control lever or valve I 55 be moved to cause hydraulic fluid pumped by the pump I I?! to be diverted to the conduit I56 and to the cylinders 48 of motors 41, the pistons of the motors ll will move upwardly to the upper limit of their strokes and when the pistons'reach this upper limit they will have displaced substantially all of the hydraulic fluid thereabove from the cylinders d8 through the conduit into the conduit it. It will be seen that when the pistons of the motors 4'! reach this upper limit of their strokes and can travel no further, the conduit I58 will be effectively blocked and therefore the pump H? would stall, thus stalling the pump I Id because both pumps 1 H and l H3 are driven from the same shaft. Accordingly I have provided a bypass circuit including a pressure relief valve It! that connects the conduits H8 and i it to by-pass the control valve unit 58. The by-pass including pressure relief valve lfii will operate when any one of the piston motors controlled by any of the individual valves of the control valve unit 56 is stalled or has reached the end of its stroke and therefore there will always be hydraulic fluid flowing in the conduit H8. It will also be seen that while the motors controlled by the valves of control valve unit 56 as herein shown are all of the double acting piston or cylinder type, if desired one or all of the motors may be of the rotary type.

From the foregoing description it will be seen that the hydraulic circuit is an improved circuit wherein at all times part or all of the hydraulic fiuid discharged from a secondary or low pressure circuit, which preferably is a control circuit including a constant volume pump, is fed to the intake port of a high pressure and preferably a variable volume pump in a main, primary, or high pressure substantially closed circuit from which hydraulic fluid is constantly being displaced as it passes or is exhausted by a high pressure reversible motor therein because of the addition of the cooling and make-up fluid thereto discharged from the secondary circuit.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and applicant therefore wishes not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of the invention, what it is desired to secure by Letters Patent of the United States is:

l. A hydraulic circuit including a relatively high volume and high pressure reversely operable pump and a reversible hydraulic motor connected in circuit therewith, said circuit including a pair of conduits one connecting the high pressure output port of said pump with the inlet port of said motor and the other connecting the low pressure intake port of said pump with the exhaust port of said motor whereby fluid in said circuit is recycled, said conduits being adapted to function alternately as high or low pressure conduits depending upon the direction of operation of said pump, pressure relief valve means, pressure operated valve means connected with both of said alternately operable conduits operated by pressure in either of said conduits acting as the high pressure conduit to connect the other conduit with said pressure relief valve means, a relatively low volume pump, conduit means includin a pair of check valves connecting the output port of said low volume pump with both of said alternately operable conduits between the ports of said high volume and high pressure pump and said pressure relief valve means, said check valves being operable to isolate said conduit from the acting high pressure conduit and to divert the entire output of the low volume pump into the acting low pressure conduit whereby the entire output volume from said low volume pump is received by said high volume and high pressure pump and the addition thereof into the acting low pressure conduit displaces hydraulic fluid discharged from said motor through the pressure relief valve means.

2. A hydraulic system including a relatively high volume and high pressure pump and a hydraulic motor connected in circuit therewith, said circuit including a high pressure conduit connecting the output port of said pump With the inlet port of said motor and a low pressure conduit connecting the exhaust port of said motor with the intake port of said pump whereby fluid in said circuit is recycled, a discharged means in said low pressure conduit, a relatively low volume pump, conduit means connecting the output port of said low volume pump with said low pressure conduit between the inlet port of said high pressure and high volume pump and the discharge conduit means therein whereby the volume of hydraulic fluid pumped into the low pressure conduit will cause displacement therefrom of some of the hydraulic fluid exhausted by said motor through said discharge conduit means, hydraulic motor means in said conduit means connecting said low volume pump with said low pressure conduit, valve means interposed in said conduit connecting said low volume pump with said low pressure conduit, said valve being adapted when inoperative to pass hydraulic fluid therethrough and when operated to divert hydraulic fluid to said hydraulic motor means and to direct the hydraulic fluid exhausted from said second motor back to said conduit means connecting said low volume pump with said low pressure conduit, and a pressure relief valve adapted to by-pass said valve means whereby the flow of hydraulic fluid into said low pressure conduit will remain substantially uninterrupted during the operation or a stalled conduit of said motor means.

FRED J. WRIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,345,920 Douglas Apr, 4, 1944 2,473,711 Kearns June 21, 1949 2,517,005 MacDuff Aug. 1, 1950 2,541,290 Robinson Feb. 13, 1951 FUREIGN PATENTS Number Country Date 234,209 Great Britain May 28, 1925 385,325 Germany Dec. 12, 15123 

